1. Field of the Invention
The present invention relates to a recording apparatus having a discoidal recording medium, and to a head control method and a recording apparatus that control the position of a head based on servo information written on the discoidal recording medium.
2. Description of the Related Art
A recording apparatus such as a hard disk drive (hereinafter, referred to as “HDD”) having a discoidal recording medium has a device called “head” that detects a magnetic signal recorded on the recording medium such as a disk and that records a magnetic signal onto the recording medium. Then, it is possible to write information and read information recorded on the disk by moving the head on the disk. The position of this head on the disk is controlled according to servo information for positioning-control, written on the disk.
FIG. 8 shows a view featuring the disk contained in the recording apparatus. FIG. 8 shows a quarter of the whole view of the disk. In FIG. 8, information recorded on a disk 1 is stored along a plurality of tracks 4.
The tracks 4 are formed as follows. A plurality of track numbers as a part of the servo information are recorded using integers in an area called servo pattern 3 shown in FIG. 8 and the tracks are formed at points 16 where the track numbers are recorded.
Therefore, the spacing between a track and a track adjacent to it (track pitch) is determined by the spacing between the points 16 where the track numbers are recorded. When the points 16 where the track numbers are recorded are spaced constantly, the tracks 4 formed have a track pitch that is equal spacing (referred to as “constant track pitch”).
Recording of the track numbers onto the disk 1 is processed as a part of writing of the servo information. This writing process of the servo information onto the disk 1 needs, as a prerequisite, use of a clean room for which dust control measures are taken. Therefore, to simplify the process and to reduce the processing time as much as possible lead to reduction of the cost of manufacture. For example, when the servo information is recorded such that the tracks have a constant track pitch, the process can be made simple and the processing time can be reduced.
However, conventionally, the servo information is written such that the track pitch is wider in the inner side and the outer side than in the area in the middle of them. FIG. 9 is a graph showing the conventional relation between the distance from the spindle and the track pitch. The axis of ordinate represents the track pitch and the axis of abscissa represents the distance from a spindle 2.
The servo information is written such that the track pitch is wide in an area 91 on the inner side and the track pitch once becomes narrower toward a point “A”, however, the track pitch again becomes wider toward an outer edge 12 from a point “B” in an area 93 on the outer side. The track pitch in an intermediate area 92 sandwiched by the areas 91 and 93 is narrower than that in the areas 91 and 93.
This is because the angle (yaw angle) formed by an tangent line 14 of a track at a point where a track number is recorded with a servo pattern and the center line 13 running through the centers of the head 5 and a head arm 7 is not zero (0) on the inner side and the outer side, and is for preventing the head from, on the outer side or the inner side, over-writing on information on a track adjacent to the correct track or reading information in a track adjacent to the correct track as the information in the correct track, due to leak magnetic field generated at the head when the yaw angle is not zero (0).
In order to realize the track pitch shown in FIG. 9, for example, in Japanese Patent Application Laid-Open Publication No. 1999-66776, a method is proposed, in which a disk is partitioned into a plurality of areas (zones) 94 in the direction of the radius and servo information is written with a varied track pitch for each zone.